A/T - Does Not Upshift When Cold

Group 24
Automatic Transmission

Bulletin Number
24 04 97

Woodcliff Lake, NJ
November 1997
Product Engineering

SUBJECT:
Transmission does not Upshift when Cold

MODEL:
E31, E32, E34, E36, E38, E39

Situation:
Customer may complain of the following:

^ Transmission does not want to upshift during the first few minutes of driving following a cold engine start.

^ Transmission upshifts at a higher road speed or higher RPM for the first few minutes of driving following a cold engine start.

^ Transmission hangs in lower gear during the first few minutes of driving following a cold engine start.

Explanation:
In order to reduce vehicle emissions immediately following a cold engine start, the engine will operate in a "warm-up" cycle until the engine operating temperature is reached. The purpose of the "warm-up" cycle is to allow the engine and catalytic converter to reach operating temperature more quickly. In order to get the engine to its operating temperature more quickly the transmission will shift at higher engine/road speeds during this time period. During the "warm-up" cycle the transmission shift points are similar to the shift points used in the "Sport" program. As a benefit to our environment, no changes to this feature are available.

NOTE:
The length of the engine "warm-up" cycle is engine temperature dependent and will therefore be extended at lower ambient temperatures. Customers should be advised accordingly.

Warranty Information:
For information only.